The present invention relates generally to internal combustion engines, and more particularly to electronically controlling engine operation through electrically operated valves, systems, and methods.
Conventional internal combustion engines include a camshaft and associated linkages to open and close intake and exhaust valves during engine operation. Since the valve timing is determined during design and manufacturing and remains fixed throughout the life of the engine, there is no room for engine performance enhancement based on variable valve timing. The fixed valve timing selected for a particular engine generally requires a compromise between engine performance, fuel economy, and emissions. It is desirable to dynamically vary valve timing based on current engine operating parameters to optimize engine performance, fuel economy, and emissions as well as to provide engine braking functions.
Although a number of approaches have been attempted for varying valve timing and engine control, many have been found impractical to implement. While hydraulic controlled valve actuators provide some benefits associated with variable valve timing, electronic or electromagnetic actuators are more versatile for a variety of applications since they allow direct electronic control of valve timing and displacement. However, prior art electromagnetic actuators that employ the movement of relatively heavy mobile permanent magnetic core or mobile coil armature assemblies require high voltages and currents to operate. For example, some prior art systems may require 42 volts or more and amperages upwards of 30 amps or more per electromagnetic actuator to operate. When many actuators are used, such as twelve actuators for a twelve-valve six-cylinder engine, the power requirements quickly become too excessive for practical implementation. In addition, in order to increase the power output of such prior art systems, a notable increase in weight of the mobile permanent magnet core or mobile coil armature assemblies is required, thereby producing a disproportionate increase in energy consumption to operate the valves. Energy efficiency of the actuator should thus be considered so that the benefits of variable valve timing are not defeated by additional power requirements of the actuator as compared to mechanical or hydromechanical systems.